Carbonate-hosted deposits of the siliceous crust type in Italy and China

摘要

The stratabound mineralization linked to the Devonian/Carboniferous carbonates of the Carnic Alps (Italy) and Central Hunan (China) is compared because of strong similarities in geological, morphological and compositional features. Mineralization occurs within a siliceous rust up to several tens of metres thick on a paleokarstic unconformity surface at the top of carbonate sequences and is transgressively overlain by siliciclastic sediments. The chemical composition is dominated by very high silica which is often associated with barite and fluorite. The metal paragenesis consists of Sb sulphides and derived oxides in Central Hunan, and of polymetallic (Zn-Pb-Cu-Sb) sulphide assemplage in the Carnic Alps. These examples highlight the characteristics of this unusual style of carbonate-hosted mineralization, represented by a stratigraphically independent, ore-bearing silicified unit.